Optical system, lens module, and terminal device

Abstract

Embodiments of the disclosure provide an optical system, a lens module, and a terminal device. The optical system includes in order from an object side to an image side along an optical axis: a first lens with a positive refractive power, the first lens having an object-side surface which is convex at the optical axis; a second lens with a refractive power; a third lens with a refractive power; a fourth lens with a positive refractive power, the fourth lens having an object-side surface which is concave at the optical axis and an image-side surface which is convex at the optical axis; and a fifth lens with a negative refractive power. The second lens has an image-side surface cemented with an object-side surface of the third lens. The optical system satisfies the following expression: 1.0 mm−1<(n2+n3)/f1.4 mm−1.

1 . An optical system, comprising a plurality of lenses arranged in order from an object side to an image side along an optical axis, the plurality of lenses comprising:
 a first lens with a positive refractive power, the first lens having an object-side surface which is convex at the optical axis;   a second lens with a refractive power;   a third lens with a refractive power;   a fourth lens with a positive refractive power, the fourth lens having an object-side surface which is concave at the optical axis and an image-side surface which is convex at the optical axis;   a fifth lens with a negative refractive power;   wherein the second lens has an image-side surface cemented with an object-side surface of the third lens, and the optical system satisfies the following expression:
   1.0 mm−1<( n 2+ n 3)/ f≤ 1.4 mm−1;
 
   wherein n2 represents a refractive index of the second lens, n3 represents a refractive index of the third lens, and f represents an effective focal length of the optical system.   
     
     
         2 . The optical system of  claim 1 , wherein an object-side surface and/or an image-side surface of the fifth lens have an inflection point. 
     
     
         3 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   −1.8< f 23/ f< 11.5;
   wherein f23 represents a composite focal length of the second lens and the third lens, and f represents the effective focal length of the optical system.   
     
     
         4 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   −3.8<(| f 2|+| f 3|)/ R 31<4.3;
   wherein f2 represents an effective focal length of the second lens, f3 represents an effective focal length of the third lens, and R31 represents a radius of curvature of an object-side surface of the third lens at the optical axis.   
     
     
         5 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   0.1< f/|f 3|<0.8;   wherein f3 represents an effective focal length of the third lens, and f represents the effective focal length of the optical system.   
     
     
         6 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   1.4<EPD/SD31<1.9;   wherein EPD represents an entrance pupil diameter of the optical system, and SD31 represents an optical effective radius of an object-side surface of the third lens.   
     
     
         7 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   5<(| f 1|+| f 2|+| f 3|)/ f< 14;   wherein f1 represents an effective focal length of the first lens, f2 represents an effective focal length of the second lens, f3 represents an effective focal length of the third lens, and f represents the effective focal length of the optical system.   
     
     
         8 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   1.2≤| R 41|/ f 4<2.9;
   wherein R41 represents a radius of curvature of an object-side surface of the fourth lens at the optical axis, and f4 represents an effective focal length of the fourth lens.   
     
     
         9 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   | R 41/ R 51|<6;   wherein R41 represents a radius of curvature of an object-side surface of the fourth lens at the optical axis, and R51 represents a radius of curvature of an object-side surface of the fifth lens at the optical axis.   
     
     
         10 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   1<(|SAG51|+SAG52)/CT5<2.5;   wherein SAG51 represents an axial distance from an intersection of an object-side surface of the fifth lens and the optical axis to a vertex of a maximum effective radius of the object-side surface of the fifth lens, SAG52 represents an axial distance from an intersection of an image-side surface of the fifth lens and the optical axis to a vertex of a maximum effective radius of the image-side surface of the fifth lens, and CT5 represents a thickness of the fifth lens along the optical axis.   
     
     
         11 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   3.4 mm<TTL<4.1 mm;   wherein TTL represents a distance from an object-side surface of the first lens to an imaging surface of the optical system along the optical axis.   
     
     
         12 . The optical system of  claim 1 , wherein the optical system satisfies the following expression:
   74°≤FOV≤92°;
   wherein FOV represents a maximum angel of view of the optical system.   
     
     
         13 . A lens module, comprising a lens barrel and an optical system, wherein the optical system is installed in the lens barrel, and the optical system comprises a plurality of lenses arranged in order from an object side to an image side along an optical axis, the plurality of lenses comprising:
 a first lens with a positive refractive power, the first lens having an object-side surface which is convex at the optical axis;   a second lens with a refractive power;   a third lens with a refractive power;   a fourth lens with a positive refractive power, the fourth lens having an object-side surface which is concave at the optical axis and an image-side surface which is convex at the optical axis;   a fifth lens with a negative refractive power;   wherein the second lens has an image-side surface cemented with an object-side surface of the third lens, and the optical system satisfies the following expression:
   1.0 mm−1<( n 2+ n 3)/ f≤ 1.4 mm−1;
 
   wherein n2 represents a refractive index of the second lens, n3 represents a refractive index of the third lens, andfrepresents an effective focal length of the optical system.   
     
     
         14 . A terminal device, comprising an lens module, wherein the lens module comprises a lens barrel and an optical system, wherein the optical system is installed in the lens barrel, and the optical system comprises a plurality of lenses arranged in order from an object side to an image side along an optical axis, the plurality of lenses comprising:
 a first lens with a positive refractive power, the first lens having an object-side surface which is convex at the optical axis;   a second lens with a refractive power;   a third lens with a refractive power;   a fourth lens with a positive refractive power, the fourth lens having an object-side surface which is concave at the optical axis and an image-side surface which is convex at the optical axis;   a fifth lens with a negative refractive power;   wherein the second lens has an image-side surface cemented with an object-side surface of the third lens, and the optical system satisfies the following expression:
   1.0 mm −1 <( n 2+ n 3) f≤ 1.4 mm −1 ; 
   wherein n2 represents a refractive index of the second lens, n3 represents a refractive index of the third lens, and f represents an effective focal length of the optical system.   
     
     
         15 . The lens module of  claim 13 , wherein an object-side surface and/or an image-side surface of the fifth lens have an inflection point. 
     
     
         16 . The lens module of  claim 13 , wherein the optical system satisfies the following expression:
   −1.8< f 23/ f< 11.5;
   wherein f23 represents a composite focal length of the second lens and the third lens, and f represents the effective focal length of the optical system.   
     
     
         17 . The lens module of  claim 13 , wherein the optical system satisfies the following expression:
   −3.8<(| f 2|+| f 3|)/ R 31<4.3;
   wherein f2 represents an effective focal length of the second lens, f3 represents an effective focal length of the third lens, and R31 represents a radius of curvature of an object-side surface of the third lens at the optical axis.   
     
     
         18 . The terminal device of  claim 14 , wherein an object-side surface and/or an image-side surface of the fifth lens have an inflection point. 
     
     
         19 . The terminal device of  claim 14 , wherein the optical system satisfies the following expression:
   −1.8< f 23/ f< 11.5;
   wherein f23 represents a composite focal length of the second lens and the third lens, and f represents the effective focal length of the optical system.   
     
     
         20 . The terminal device of  claim 14 , wherein the optical system satisfies the following expression:
   −3.8<(| f 2|+| f 3|)/ R 31<4.3;
   wherein f2 represents an effective focal length of the second lens, f3 represents an effective focal length of the third lens, and R31 represents a radius of curvature of an object-side surface of the third lens at the optical axis.